grateing noise on overrun

[triumphelan]

I have just noticed a"grateing noise" on overrun,never when on power or tickover .It is only there when in gear .I have had a look under, propshaft feels ok,diff unit is all tight input/output flanges I can feel no play,I have TT splined drive shafts they are ok .Any thoughts ??

[john.p.clegg]

I was going to say check the u/j's.
Seeing it is on the over-run why dont you jack up the back end and spin the wheels in neutral i.e. recreating the over-run
John

[types26/36]

[quote="triumphelan"]I have just noticed a"grateing noise" on overrun,never when on power or tickover .It is only there when in gear .Iquote]

John,
If I remember correctly you just had some problems with the exhaust system, I would check that your exhaust system (particularly around the manifold...headers) are not touching the chassis, failing that check the diff is not touching the chassis at the lower point.
Brian

[triumphelan]

It dose`nt happen in neutral,only on overrun in gear .
I have had the car on axial stands the exhaust is not touching anywhere,the diff is clear of the chaissis,
Is ther any test I can do to the gearbox and diff to dissmiss them ??

[type26owner]

Make sure the timing chain slack is correct.

[types26/36]

I know you said the exhaust is not touching but is there enough clearance as the the engine/transmission/diff shift under differing conditions, I also had a similar noise which turned out to be the manifold touching under deceleration even though it was not touching in a steady state.
Brian

[type26owner]

I brazed in a brace to the bracket on the chassis for the engine mount on the exhaust side of the engine. Completely forgetting about the expansion can in the exhaust downpipe. The can of course hit the brace under acceleration. On my engine on overrun the exhaust moves away from the chassis.

If you stand in front of the car facing it, the reaction force of engine against it's mounts under full throttle will cause it to rotate counter-clockwise or by the right-hand rule. Most crankshafts go clockwise and are left-handed. (This assumes your thumb is pointed in the forward direction of travel.)

That's not so bad. On a 62 Corvette both sides of the dual exhaust run through openings in the chassis. Have it off by just a midge and it hits both when accelerating or on overruns! Now that's a design feature!

[triumphelan]

I have been worrying about posible gearbox/diff problems ,but as Brian said I have been playing with the exhaust I have tried to get the rear box as high as I can, I will give it a good looking at today

[triumphelan]

Could not fault exhaust set up.BUT put my listerning rod onto alternator it sounded like a bag of nails ,"bearings" ?? I thought but I have only just had a recon alternator.removed the alternator and it spun and there was no undue bearing noise whilst on the bench.I have Vulcan toothbelt drive to the waterpump/alternator and the belt was schreaded,most not all the teeth were missing .Awaiting new belt will let you know the outcome

[Dave-M]

Just had this problem on my +2, It turned out to be a knackered engine mount (carb side). Not only was there metal to metal contact in the mount but also air box to inner wing contact. It made a terrible noise. I swapped the mount and away it went. Remember the mounts are handed. Mine had the wrong one fitted and now has the correct one.
Regards
Dave

[triumphelan]

Fitted new belt ,test ok no noise